The GetKey functions queries keyboard keys using a specific convention, or the KeyCode enum.
If you are trying to query a key set in the Input Manager, then you should be using the GetButton Input functions. These axes are not accessible through the GetKey functions.
It is much easier to use the input function overloads that take a KeyCode.
Keycodes are autocompleted by your IDE1, so they don't require documentation to use.
If you're not okay with switching to KeyCode, see the mapping virtual axes to controls section for the correct naming conventions of keys.
Capitalisation is important. Uppercase keys will be unknown.
Check IDE configuration if you don't have autocomplete.↩